Field of the Disclosure
The present disclosure relates to a liquid crystal display device, and more particularly, to a polarizer and a display device including the same that have a light-absorption layer absorbing at a specific wavelength and a wide color gamut.
Discussion of the Related Art
A liquid crystal display (LCD) device includes two substrates and a liquid crystal layer between the two substrates and transmits light by controlling an arrangement of liquid crystal molecules of the liquid crystal layer, thereby displaying an image.
In general, the LCD device includes a plurality of pixels arranged in a matrix form, and each pixel includes a thin film transistor, a pixel electrode and a common electrode. Voltages are applied to the pixel electrode and the common electrode of each pixel, and an electric field is generated between the pixel electrode and the common electrode. The liquid crystal molecules of the liquid crystal layer are rearranged by the generated electric field, and the transmittance of the liquid crystal layer is changed. Therefore, by adjusting the voltages applied to the pixel electrode and the common electrode of the LCD device, the transmittance of the liquid crystal layer of each pixel can be controlled to produce a value corresponding to an image signal. As a result, the LCD device displays an image.
The LCD device is not self-luminous, and thus additional light should be provided to the LCD device. Accordingly, the LCD device includes a liquid crystal panel displaying the image and a backlight unit providing light to the liquid crystal panel.
The backlight unit includes a light source. A fluorescent lamp such as a cold cathode fluorescent lamp (CCFL) or an external electrode fluorescent lamp (EEFL) has been used for the light source.
The backlight unit is classified as a direct-type or an edge-type depending on the path of light emitted from the light source. In a direct-type backlight unit, a plurality of lamps is disposed under the liquid crystal panel, and light emitted from the lamp is directly provided to the liquid crystal panel. In an edge-type backlight unit, a light guide plate is disposed under the liquid crystal panel and a lamp is disposed at at least one side of the light guide plate. Then, light emitted from the lamp is refracted and reflected by the light guide plate and is indirectly provided to the liquid crystal panel.
Recently, the edge-type backlight unit has been widely used in accordance with the request for a thin and light weight LCD device, and a light emitting diode (LED) lamp has replaced the fluorescent lamp because of its advantages in power consumption, weight and brightness.
FIG. 1 is a schematic cross-sectional view of an LCD device including an edge-type backlight unit according to the related art.
In FIG. 1, the related art LCD device includes a liquid crystal panel 10, a backlight unit 20, a main frame 30, a top frame 40, and a bottom frame 50.
The liquid crystal panel 10 includes a lower substrate 12 and an upper substrate 14, and a liquid crystal layer (not shown) is disposed between the substrates 12 and 14. A lower polarizer 18 is disposed under the lower substrate 12, and an upper polarizer 19 is disposed over the upper substrate 14.
A driving unit (not shown) comprising driver integrated circuits (driver ICs) is connected to a side of the liquid crystal panel 10 and provides signals to a plurality of pixels (not shown) in the liquid crystal panel 10.
The backlight unit 20 is disposed under the liquid crystal panel 10 and includes a reflective sheet 22, a light guide plate 24, and an optical sheet 26 sequentially placed from the bottom. Meanwhile, a light emitting diode (LED) assembly 28 is disposed at a side of the light guide plate 24 as a light source. The LED assembly 28 includes an LED printed circuit board 28a and an LED package 28b. 
The main frame 30 surrounds sides of the liquid crystal panel 10 and the backlight unit 20. The main frame 30 constitutes a module with the top frame 40 at a front side of the liquid crystal panel 10 and the bottom frame 50 at a rear side of the backlight unit 20.
Since the related art LCD device has a relatively low color gamut, the related art LCD device does not express relatively more colors, and it is difficult to display a high-quality image.
FIG. 2 is a view illustrating the color gamut of a related art LCD device in CIE (International Commission on Illumination) 1976 chromaticity diagram. FIG. 2 also shows the DCI (digital cinema initiative) color standard.
Generally, to attain a wide color gamut, an overlap ratio of the color gamut of a display device to the DCI color standard should be more than 95%. However, as shown in FIG. 2, the color gamut NCG of the related art LCD device has a smaller area than the DCI color standard, and the overlap ratio is about 81.0%. Therefore, it is difficult that the related art LCD device has a relatively wide color gamut.